1. Field of the Invention
This invention relates to a lens barrel having a cam member.
2. Description of the Related Art
Heretofore, the zoom lens barrel of the kind called a short zoom lens has been composed of a mount, a fixed tube, a cam tube, a zoom operation ring, etc.
However, the conventional zoom lens barrel of the above-stated kind has necessitated the use of a guide tube which is provided with a guide groove for zoom-moving a lens carrying frame in conjunction with the cam tube. Further, the cam tube and the zoom operation ring have been arranged separately from each other. The conventional arrangement of these parts leaves much room for reduction in manufacturing cost.
Further, it has been necessary for the conventional lens barrel to have a mechanism for adjustment of a flange focal distance (a back focal distance). For example, it is generally practiced to measure the degree of error of the flange focal distance and to insert in between the mount and the fixed tube a washer having a thickness corresponding to the measured degree of error. In accordance with this method, however, it is difficult to continuously vary the degree of adjustment. Besides, the method necessitates the washer to be kept in stock in many different kinds. This has presented an inconvenience with respect to management of parts.